JP2000075601A - Electrifying roller type electrophotographic copying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic copying device in which the electrifying roll touches the photosensitive drum by surface contact under weak pressure so that the durability of the device is increased and stable long-run traveling is realized. SOLUTION: The electrifying roller 1 is an endless tubular film made of a polyamide elastomer having 103 to 1013 Ω/(square) surface resistance. The roller disposed to give surface contact with 1.5 to 7 mm contact width with the photoreceptor during copying. The endless tubular film made of a polyamide elastomer above described is preferably suspended by a conductive roller consisting of a metal core roller and a conductive foamed body deposited around the core.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roller type electrophotographic copying machine, and more particularly to a charging roller.

[0002]

2. Description of the Related Art In an electrophotographic copying apparatus for copying and printing using a conventionally used toner, first, a copying operation process starts with an operation of charging a photosensitive member (generally in the form of a drum). When the operation is performed by air discharge, generation of ozone is unavoidable, which has been a problem from the viewpoint of environmental pollution. As one of the solutions, a charging roller system has been developed in which a charging roller is brought into contact with a photoreceptor to transfer and charge a charge.

In a method of charging a photoreceptor using a charging roller, a photoreceptor is brought into contact with a charged cylindrical charging member to move electric charges to charge the photoreceptor.
Ozone generation is suppressed.

[0004] In the conventional charging roller in which the charging member is formed in a cylindrical shape, there are two typical application states of the charging member: a film-type application method and a brush-type application method. In this embodiment, a semiconductive synthetic resin film is wound and attached to an aluminum tube (core) via a conductive rubber layer (hereinafter, referred to as a film roll), and is used as a brush. In an embodiment in which the present invention is applied, a staple fiber of a semiconductive synthetic fiber is uniformly electrodeposited on the outer periphery of an aluminum tube core by an electrostatic flocking technique (a so-called flocky processing method) (hereinafter, referred to as a brush roll). Used.

However, both the film roll and the brush roll systems have the following problems and cannot provide a satisfactory result. That is,
Copy area (especially width) in the film roll method
It is difficult to maintain uniform contact pressure between the photoreceptor and the film roll due to the increase of the photoreceptor, and it is easy to cause electrification unevenness. Also, the photoreceptor is easily worn due to the mechanism in which the structurally rigid film is in rotational contact with the photoreceptor In addition, since it is easily damaged, care must be taken to reduce the contact area as much as possible to avoid such problems.
It is designed to contact in line contact state, but on the other hand, this countermeasure backfires and a decrease in contact width lowers charging efficiency and induces a corona-like charging state, thus suppressing the target ozone generation In addition, the danger of surface deterioration of the roll itself increases when a higher voltage is applied. Therefore, it is necessary to search for a compromise (of the contact width) and to design the roll. There was a drawback that only devices that easily occurred could be manufactured.

[0006] On the other hand, the brush roll method is also required in terms of selecting the optimum bending hardness and thickness of the fibers forming the brush, and ensuring optimum and even flocking length and density. It is difficult to manufacture a product in which the conditions are adjusted to the optimum condition, and it is difficult to find and set the optimum charging conditions and operate the device equipped with such a charging device. Also, if the bending hardness of the flocking fiber is too high or the rotation speed is too fast, the photoreceptor is easily damaged, the occurrence of dropping of the flocking fiber cannot be completely prevented, and it is difficult to secure a very uniform flocking density. There were also problems in terms of the device life and the uniform charge maintenance. Further, in the case of contact in the cross section of the fiber, the electric resistance of the fiber is determined by the volume resistance value, but the contact charging under the volume resistance value is inferior in the stability of the resistance. That is, the resistance characteristic is apt to change due to a change in environment or a change with time. This is probably because, in the case of conductive powder dispersed in the fiber, for example, carbon black, the powder moves inside the fiber surface and changes the dispersion state. In addition to the above two methods, image defects due to pinhole defects on the photoreceptor surface are likely to occur. Therefore, it is necessary to strictly control the use of a photosensitive member having no defect.

As a novel means for improving the defect in the above two known charging means, the present inventors have previously developed a method using a polyamide elastomer for contact charging, applied for a patent, and have already filed a patent application. It was published in Japanese Patent Publication No. 9-230673. The technology disclosed in the invention selects a polyamide elastomer as a charging roll material, and disperses and kneads a conductive agent, preferably carbon black, with the polyamide elastomer, and gives the elastomer a volume resistance value of 10 ³ to 10 ¹² Ω · cm. Then, the sheet is cut into a predetermined size, and the cross section thereof is brought into contact with the surface of the photoreceptor to charge the photoreceptor.

[0008]

The electrophotographic copying apparatus based on the invention disclosed in the above-mentioned publication is superior to the conventionally known charging roller type electrophotographic copying apparatus in that it eliminates many defects of those apparatuses. It has already been tried for practical use, but in the long run test at the stage of practical use test, a point to be solved further in terms of durability was discovered,
The solution turned out to be essential.

[0009] That is, although there is almost no problem in practical use at the time of copying 5,000 sheets, slight streak-like density unevenness is seen in the copied and printed image, and when the 10,000th sheet is reached, the sheet becomes dark. Although a small amount of toner adheres to the photoreceptor around the contact portion, the sheet starts to be cut off and the leading end of the sheet starts to be scraped. This phenomenon is
Due to the charging due to line contact in the cross section of the thin sheet, every time a voltage was applied, the state of dispersion of carbon black at the tip changed due to the concentration of all of the charges at the tip, causing a change in the volume resistance value. In other words, it is considered that the phenomenon occurs because the resin itself serving as the matrix has started to deteriorate.

Therefore, the inventors of the present invention have started to study a solution based on the technology disclosed in Japanese Patent Application Laid-Open No. 9-230673 to solve this problem, and the problem can be solved by the following means. This led to the present invention.

[0011]

That is, as a method for solving the problem, in a charging roller type electrophotographic copying apparatus as defined in the claims of the present invention, the charging roller is set to 10 ³ Ω to 10 ¹³ Ω. An endless tubular film of a polyamide elastomer having a surface resistance of // and a contact width with a photoreceptor during copying of 1.5 to 7
By using a charging roller type electrophotographic copying apparatus provided with a surface contact of mm, a device capable of copying with excellent image quality stably for a long time can be obtained.

Further, in claims 2 to 4, specific examples of particularly preferred embodiments of the charging roller type electrophotographic copying apparatus defined in claim 1 have been disclosed and provided.
That is, (1) In the second aspect, the structure of the charging roller in the charging roller type electrophotographic copying apparatus defined in the first aspect is obtained by winding an endless tubular film of a polyamide elastomer on a metal core roller with a conductive foam. Stipulated to be suspended from a conductive roller. (2) Claim 3 specifies that the charging roller according to claim 1 or 2 is made of an endless tubular film of a polyamide elastomer containing 5 to 30% by weight of carbon black. (3) In the fourth aspect, the endless tubular film of the polyamide elastomer for a charging roller according to any one of the first to third aspects, wherein the endless tubular film is mainly composed of a segment comprising nylon 12 segments and a polyalkylene glycol. It is specified that it is composed of block amide elastomer.

That is, the present invention provides a problem in the mechanism of a conventional charging roller type electrophotographic copying apparatus, in which a hard charging roll is brought into line contact with a photosensitive drum in order to charge the photosensitive drum without generating ozone. Abrasion damage on the surface of the photosensitive drum, unevenness and concentration of charge density at the end (joint) of the semiconductive sheet of the charging roll, and drum-roll caused by the mechanism for transferring and transferring the charge by pressing against the photosensitive drum In order to eliminate problems such as the occurrence of charge unevenness due to uneven contact pressure of the contact portion, the charging roll is made of a soft endless tubular film having a low bending elastic modulus and a compressive elasticity to make contact with the photosensitive drum. Utilizing the electrostatic attraction force by charging the endless tubular film that forms the charging roll, we developed a device that makes contact with the photosensitive drum with low contact pressure in surface contact. All, which has been a problem it was to solve the problems. Further, the present invention, as an endless tubular film constituting material for constituting a charging roll satisfying the above functions,
By selecting a polyamide elastomer, not only the above mechanical requirements can be satisfied, but also the electrical performance required for the charging roll material can be satisfied at the highest level, and the charging roller type has high performance, high stability and high durability. The company succeeded in providing an electrophotographic copying machine.

More specifically, the structure of a conventional charging roller type electrophotographic copying machine has the structure shown in the schematic side sectional view of FIG. That is, the photosensitive drum 21 and the charging roll 22 for transferring and charging the electric charge to the photosensitive drum (charging to +) are disposed so as to be in contact with the surface of the photosensitive drum 21 with a contact width of about 1 mm in the arrangement shown. .
The charging roll 22 uses an aluminum tube as a core material,
A conductive rubber is wound around the periphery, and an insulating thin layer such as a fluoro resin is wound around the rubber sheet. The charging roll 22 is connected to a variable current power supply 23 via a voltmeter 24 with a lead wire drawn out of a core aluminum tube, is supplied with a required voltage and is charged, and is charged through a contact surface between the charging roll and the photosensitive drum. The charge is transferred to the surface of the photosensitive drum, and the charge is supplied to the surface of the photosensitive drum to be charged.

Next, the original to be copied is exposed to an exposure device 2.
5, the image to be copied is formed on the photosensitive drum 21 to form an electrostatic latent image, toner is supplied to the electrostatic latent image from the developing device 26, and the electrostatic latent image is changed to a toner visible image. The image is transferred onto a sheet 28 supplied by a drum 27 to obtain a copy sheet 29. After the copying is completed, all the remaining charges are removed by the charge remover 30, and the remaining toner is also removed and cleaned by the toner cleaner 31, thereby completing the copying process. The above is the cycle, and the copying process is repeated starting from charging again.

According to the present invention, in order to eliminate the defect of the electrophotographic copying machine of the conventional basic structure of the charging roller type, the following measures are taken, and the following functions which cannot be obtained without the prior art are provided. Is given. A semiconductive material that constitutes the surface charged body of the charging roll in order to prevent damage to the photosensitive drum, which is extremely sensitive and susceptible to damage, and requires high precision, and to enable transfer and transfer of charges with high efficiency. The polymer is changed to an endless tubular film of polyamide elastomer (polyether block amide elastomer), which is richer in compression elasticity and more flexible and softer than the conventional high-hardness synthetic resin film.
Efficient transfer and transfer of electric charge, prevention of damage to the photosensitive drum, and extension of service life have been achieved.

The charging roller is made of an endless tubular film, and the existence of a cut surface is eliminated from the surface layer sheet of the charging roll. By applying a high voltage, all of the electric charge is concentrated at the front end of the cut surface of the sheet, and the carbon black is dispersed at the front end. By changing the state, the possibility of the volume resistance value fluctuating and the possibility of the deterioration of the resin itself forming the matrix itself being eliminated were eliminated, and the long-term stable performance of the charging roll was successfully maintained. The charging roller is rich in compression elasticity and is made of a more flexible and soft polyamide elastomer endless tubular film.
The endless tubular film for charging has a predetermined width on the photosensitive drum (the contact width is 1.
(To make a surface contact of 5 to 7 mm) by suction and contact, and it is possible to transfer and transfer the charge to the photosensitive drum with high efficiency.

The application of an endless tubular film of a polyamide elastomer (polyether block amide elastomer) to the charging roll does not itself satisfy the surface resistance required for transferring and transferring the charge from the charging roll to the photosensitive drum. Therefore, by adding and kneading a conductive agent such as carbon black to the polyamide elastomer, essential electric performance such as an optimum surface resistance value (10 ³ to 10 ¹³ Ω / □) can be arbitrarily and easily imparted, and a long term It has made possible to produce a high-performance charging roll that can maintain stable performance over a long period of time.

The significance of giving a predetermined surface resistance value to a charging roll, which is particularly important in the above-described apparatus configuration, will be described. In a charging roller type electrophotographic copying apparatus, the surface resistance value is determined by charging a photosensitive drum with a charge. High efficiency, quick
It is an essential function for transferring and transferring accurately and performing stable high-quality copying. As a specific preferable value, the surface resistance value is in the range of 10 ³ to 10 ¹³ Ω / □. is necessary. This is because, if the surface resistance is lower than 10 ³ Ω / □, the charge density tends to decrease and the density of the copied image (particularly, the solid portion) tends to be low. This is considered to be because when the surface resistance value is low, a current is generated and the current easily flows and disappears. On the other hand, if the surface resistance value is higher than 10 ¹³ Ω / □, the charging efficiency is reduced, and the surface of the endless tubular film is heated,
Further, corona discharge is caused from the surface. It is considered that these phenomena tend to be caused by the fact that all the applied voltage is not consumed for charging the photoreceptor, but is gradually charged.

In the size (tube diameter, thickness, width) of the endless tubular film, first, regarding the tube diameter and width, the size and mounting method of the conductive roll base, that is, fitting the conductive roll base to the roll base, and firmly fitting It is different depending on whether it is used in a fixed state or in a state of being suspended on the roll base shown as a preferred form in the present invention. On the other hand, for the thickness,
In order to perform efficient charging with a more stable surface resistance, it is preferable that the thickness is thinner than the thicker one.However, durability based on its own strength, attachment to the roll base, running stability, and It is preferable to perform the setting in a well-balanced manner in consideration of the manner of mounting. To illustrate the thickness from such a point, the thickness of the endless tubular film constituting the charging roll is about 0.05 to 1 mm, preferably about 0.07 mm.
0.7 mm is preferable.

The contact width between the endless tubular film and the photosensitive drum constituting the charging roll is 1.5 to 7 m.
m, preferably 2 to 6 mm, more preferably 3 to 5 m
The distance between the charging roll and the photosensitive drum is set such that the distance is m. Although the present invention is not a charging means in line contact (kiss-touch-like) performed by a conventional charging roller, it is also a semi-conductive polyamide elastomer endless tubular film having the above-mentioned characteristics to be charged in a surface contact state, It is even more efficiently achieved for the first time, subject to the contact width. This is because in the present invention, in addition to the charging efficiency, the object is to exert a more excellent effect also on durability (surface resistance fluctuation due to surface deterioration caused by abrasion-image deterioration) due to wear itself. . Since both these effects are simultaneously expressed, it is necessary to specify the contact width. If the width is less than 1.5 mm, the charging efficiency tends to decrease and ozone tends to be generated. Conversely, if the width exceeds 7 mm, the charging efficiency does not decrease, but the durability decreases. There is a tendency. Further, in the rotation of contact with the photoreceptor, there is a risk that the surface contact becomes non-uniform, so that it must be avoided.

The surface contact width may be provided at least at the time of copying. Therefore, the charging roll may be arranged in surface contact with the photosensitive member from before the copying operation. It may be arranged away from the camera. As described above, if the contact width is smaller than the above specification, the efficiency of the charge transfer delivery surface is reduced, and if the contact width is too large, a problem may occur in running stability and durability. By applying the constituent features of the present invention, it is possible to obtain a high-performance charging roller type electrophotographic copying apparatus capable of maintaining excellent functions for a long period of time.

In the present invention, the above-mentioned conventional charging roller is specified in place of the above-mentioned charging roller, but it is 10 ³ to 10 ¹³ Ω / □, preferably 10 ⁵ to 10 ¹¹ Ω, which forms the basis of the roller.
/ □, more preferably 10 ⁶ to 10 ⁹ Ω / □, the polyamide elastomer endless tubular film having the following surface resistance is as follows.

First, the polyamide elastomer, which is a material, has a non-rubber-like elasticity and high hardness (Shore D hardness of about 6).
Different from various thermoplastic resins such as Nylon-based resin, the rubber-based elasticity is imparted to the Nylon-based resin by a chemical method, and low hardness (about 45 or more in Shore A hardness, Shore D hardness) , About 60 or less), and a thermoplastic non-vulcanized polyamide rubber elastic resin. However, the elasticity of the elastomer is within the range of elastic after-effect deformation, and is different from that close to the ideal elastic deformation as seen in natural rubber and synthetic rubber.

The polyamide elastomer (polyether block amide) is a thermoplastic elastomer (TPE) composed of polyamide as a hard segment and polyalkylene glycol as a soft segment. It is a block copolymer indicated by. That is,-[-
(Ny) -NHCO-R ₁ -CONH- (R ₂ O) n-] m
-(Where Ny: polyamide segment, R ₁ , R ₂ :
Here, the hard segment component is generally composed of an aliphatic polyamide or an aromatic polyamide component such as nylon 6, 66, 610, 11, 12 or the like, and the soft segment is a soft component having entropic elasticity. For example, an aliphatic polyether or aliphatic polyester component. Various combinations can be made depending on each of these segment components, whereby the rubber elasticity can be changed or the hardness can be changed. Further, as an attempt of softening, for example, in an aliphatic polyamide of a hard segment component, the amide group is reacted with an alkylene oxide such as formaldehyde or ethylene oxide or propylene oxide to form an alkylol such as a methylol or ethylol or a petrol. May be used.

The subject of the present invention is achieved with the polyamide elastomer according to the present invention in any combination with any of the above-mentioned components. Therefore, although not specified, aliphatic polyamide components and aliphatic polyether components are not specified. The effect can be seen to be improved by those in the range of aliphatic polyamide ether elastomers formed by the combination of Further, the present invention relates to an aliphatic polyamide component forming a hard segment portion, which comprises polyamide 12
When the (Nylon 12) segment is specified, further improvement effects can be seen. In other words, by using the polyamide 12 as a segment, an endless tubular film having more stable electric resistance characteristics is obtained, and further, the durability (strength, dimensional stability, etc.) is excellent, and the environment (humidity, temperature) is improved. Can be said to be more excellent in that it has various characteristics such as an extremely small influence of the above.

The method for producing the polyamide elastomer is not particularly limited, since it is produced by a generally known method. As the production method, for example, in the case where polyamide 12 exemplified as the more preferable one is used as a hard segment, a mixture of a terminal aminated polyalkylene ether glycol and an equivalent amount of an aliphatic dicarboxylic acid and ω-laurolactam is treated with nylon. It is obtained by polymerizing under mold conditions.

The polyamide elastomer particularly has a surface resistance value of 10 ³ to 10 ¹³ Ω / □ and is in the form of an endless tubular film. First, the electric resistance characteristic is specified by the surface electric resistance. The reason for this is that the photosensitive member is charged on the surface of the endless tubular film. Therefore, it is necessary to stably maintain the electric resistance value of at least the surface layer portion and maintain the desired value. By using a polyamide elastomer as a raw material, a more stable electric resistance characteristic not found in other synthetic resins can be exhibited. Maintaining a stable surface resistance value for a long time means that high-quality copying can be stably performed for a long time.

The significance of the surface resistance is as described above. However, in order to charge the photosensitive member quickly and efficiently, a specific resistance value in the range of 10 ³ to 10 ¹³ Ω / □ is required. Is achieved only when And the polyamide elastomer having the surface resistance value is in an endless tubular film shape, but by being used as a charging roller in this shape, first of all, compared to the brush-like or sheet-like charging method, for charging, Is not concentrated at one point throughout the charging operation, but is kept charged uniformly with a predetermined width. As a result, more stable charging can be maintained for a long time, and no physical damage such as cracks is caused on the surface. That is, the result is more excellent in durability. In addition, since there is no joint, there is no danger of being cut by rotation, not being able to rotate smoothly, or causing uneven charging.
Further, in terms of manufacturing the charging roll, the tubular film can be easily manufactured simply by fitting the tubular film to the conductive roll base, so that it is possible to always obtain a stable quality with the manufacturing time.

Next, a method for producing a polyamide elastomer endless tubular film having a surface resistance value of 10 ³ to 10 ¹³ Ω / □ will be described. First, 5 to 30 conductive powders are added to the polyamide elastomer (pellet or powder).
% By weight (based on polyamide elastomer powder), preferably 10 to 25% by weight. In this case, the means of dispersion is the most efficient method between the elastomer and the conductive powder. However, it is preferable that the mixture is once mixed by a high mixer or the like and then melt-kneaded by a twin screw extruder. It is preferable that the pelletized product is provided to the next tubular film forming machine. Here, the conductive powder generally has a particle size of 1 to 50.
More specifically, carbon-based and metal-based powders of about 0 μm include carbon black and carbon fiber,
Examples of the metal system include aluminum, silver, copper, zinc oxide, and indium tin. Other examples include titanate whiskers and carbon whiskers.

As the conductive powder, an optimum one is selected in consideration of the mixing dispersibility (compatibility) with the polyamide elastomer, the moldability, the stability after molding (electrical resistance characteristics), and the like. Among these, carbon black is preferable. In addition, even if it says carbon black,
There are various types depending on the difference of the raw material source. It is acetylene black, channel black, furnace black, thermal black or the like, among which acetylene black or furnace black is more preferable. In addition, in the case of this mixing, it is permissible to select an effective one from various commonly known additives, to add a small amount (a range that does not change the essence of the present invention), and to use them together.

Then, the obtained mixture (powder or pellet) is fed into an extruder equipped with an annular die (temperature is generally 15
(0-250 ° C.) and extruded into an endless tubular film. Here, the molding conditions (temperature, discharge pressure,
The discharge speed, stretching, etc.) may be determined as an experimental form, but it is preferable to determine in advance the detailed conditions by checking in advance the relationship with the variation in the surface resistance value.

The copying by the electrophotographic copying apparatus according to the present invention includes not only a single color but also a plurality of colors, and has the same effect on each color toner.

Ultimately, the significance and effect of selecting the polyamide elastomer are as follows. The greatest required function of the charging roll material is that the charge on the roll surface is brought into close contact with the photosensitive drum and the charge is efficiently transferred without damaging the photosensitive drum. Because it can be transferred and transferred well, it has an appropriate hardness (Shore A hardness: 45 or more, Shore D hardness: 60 or less) that does not wear or damage the photosensitive drum surface, and an appropriate bending elastic modulus (5, 00
(0 kgf / cm ² or less), and it must have compression elasticity. Polyamide elastomer is an elastomer that satisfies this condition, and it is possible to change physical properties such as compression elasticity and hardness by its copolymer composition. Therefore, the ability to respond to required functions by selecting a copolymer having a copolymer composition according to the purpose is high.

Since the charging roll material is a roll for transferring and transferring electric charges to and from the photosensitive drum, it has excellent electrical characteristics, particularly a surface resistance value (10 ³ to 10) which is essential for charge transfer.
¹³ Ω / □, more preferably 10 ⁶ to 10 ⁹ Ω / □), but the polyamide elastomer is a polymer that has a certain level of satisfying such electrical properties. Acetylene black, channel black, thermal black, etc.)
And various conductive fine powders such as fine metal powders or titanate whiskers (5 to 30% by weight) are added and kneaded to prepare and produce a polyamide elastomer having any desired optimum electrical characteristics. It is possible, and the kneading technique has already been established as a general-purpose technique, and is an optimal material (polymer) from this viewpoint in order to achieve the object.

The polyamide elastomer is one of the thermoplastic elastomers (TPE) as described above, and can be extruded and injection-molded into a molded article having an arbitrary shape using existing general-purpose equipment. Extrusion molding technology into a tubular material of arbitrary thickness and arbitrary diameter for manufacturing a certain endless tubular film is already fully equipped as a general-purpose technology, and it is extremely easy to produce a desired endless tubular film of uniform arbitrary thickness and diameter. There is an advantage that it can be manufactured.

As described above, the properties of the polyamide elastomer can be modified by selecting the copolymer composition (constituent components) of the block copolymer, regardless of the hard segment / soft segment.
In general, it is known that the use of a monomer unit having a long chain length makes it possible to obtain a polymer having lower hardness, rigidity and elastic modulus by introducing a side chain. -It is also known that the block copolymerization ratio changes the elastic performance, so that there is an advantage that the copolymer according to the purpose can be arbitrarily selected by appropriately selecting the copolymer composition. In the embodiment of the present invention, nylon 12 is selected as a hard segment from an appropriate aspect such as flexibility in electrical characteristics, but the present invention is not limited to this.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The specific specifications of the charging roller type electrophotographic copying machine of the present invention will be described below.
In FIG. 1, reference numeral 2 denotes a conductive rubber sponge roll having an aluminum tube as a core, and has a surface resistance value of 10 according to the present invention.
A polyamide elastomer endless tubular film 1 having ³ to 10 ¹³ Ω / □ is suspended and mounted to form a charging roll, and is disposed to face the photosensitive drum 3. The tubular film 1 is not in contact with the photosensitive drum 3 (small gap). When the application of a predetermined voltage by the variable DC power supply 4 to charge the photosensitive drum 3 is started, the suspended tubular film 1 is attracted to the photosensitive drum 3 by surface contact (W = 1.5 to 7 mm) and charged. (+ Charge). While maintaining this surface contact width, the tubular film 1 is connected to the conductive rubber sponge roll 2 (generally free rotation) in conjunction with the rotation of the photosensitive drum 3. Good), and charge while rotating. When the predetermined copying is completed and the voltage application is stopped, the tubular film 1 separates and returns to the original position. The power supply 4 has a lead wire terminal connected to an electrode provided on a side surface of an aluminum tube as a core via a voltmeter 4a. In addition, 5, 6, 7, 8 (8a), 9 and 10
Numerals denote an exposure unit, a development unit, a transfer drum, a copy sheet, a static eliminator, and a toner cleaner corresponding to FIG.

FIGS. 2 to 4 show another example of the arrangement state with a partial view of FIG. That is, FIG.
In the state in which the charging roll 11 made of the endless tubular film is fitted and fixed to the conductive rubber sponge roll 10 manufactured by the above configuration, charging is started so that the charging roll 11 has a predetermined surface contact width (W). This is the case where they are physically pressed before and arranged. When the width is set to a predetermined value, a voltage is applied to guide the photosensitive drum 3 to charging via the charging roll 11, but the rotation of the photosensitive drum causes the charging roll to rotate in conjunction with the photosensitive drum 3 and keep charging at a constant charging potential during copying. Incidentally, the charging roll may be a free rotation or an automatic synchronous rotation mechanism with the photosensitive drum. In addition, it is preferable to incorporate a detachable mechanism for the photosensitive drum from the viewpoint of contact width adjustment.

FIG. 3 shows one application of FIG. 1, wherein two conductive rubber sponge rolls 12, 1 are arranged in a vertical position.
2 is a belt-shaped charging roller in which the endless tubular film 13 is fitted in a belt shape, which is opposed to the photosensitive drum 3 and is arranged with a small gap. Here, the small gap is the distance at which the endless tubular film 13 is easily attracted to the surface of the photosensitive drum 3 by the electrostatic attraction generated by the application of a voltage as in FIG. The specific numerical value depends on, for example, the thickness (flexibility) of the endless tubular film 13, the surface resistance value, the applied voltage, and the like. Cannot be exemplified. In FIG. 3, the wiring is such that a voltage is applied to both the conductive rubber sponge rolls 12 at the same time, but either one may be used.

Further, FIG. 4 shows that the endless tubular film 15 moves the charging roll suspended on the conductive rubber sponge roll 14 in the state as shown in FIG. A predetermined surface contact width (W) for the photosensitive drum 3
Shows a case where the members are physically pressed and arranged. The tubular film 15 is interlocked with the sponge roll 14 by the rotation of the photosensitive drum 3. At this time, the sponge roll 14 has a mechanism of either free rotation or automatic rotation with the photosensitive drum 3. Take. It is preferable to incorporate a detachable mechanism for the photosensitive drum 3 as in FIG. It should be noted that, since the tubular film 15 is longer and can be fitted with respect to FIG. 2, the present embodiment is a more preferable structure from that point.

In FIG. 1, the conductive roll base on which the endless tubular film is mounted is exemplified by a core formed of an aluminum tube and a conductive rubber sponge wound thereon. Instead of an aluminum tube, another metal tube may be used, and instead of the conductive rubber sponge, a non-sponge conductive rubber sheet, a conductive nonwoven fabric or a felt or a composite material in which these are appropriately combined are wound. The conductive roll may be a base roll. The hardness of the material to be wound and the hardness of the conductive roll substrate obtained by winding can be generally exemplified by a rubber hardness (Shore A) of about 10 to 50. It is better to decide as a preliminary test on the premise that it effectively contributes to efficiency, durability and the like.

In the above embodiment, a conductive roll core on which an endless tubular film is mounted is exemplified by an aluminum tube as a core material and a conductive sponge wound thereon. There is no need to limit to aluminum at all, any conductive metal tube may be used, and the conductive rubber sponge layer does not need to be a rubber sponge at all. Any material may be used, and any material obtained by winding a conductive felt, a conductive elastomer, or the like on a core material may be used.

[0044]

EXAMPLES The technical contents and embodiments of the present invention will be described below in more detail with reference to Examples. [Example 1] Powder of polyether polyamide resin dried with nylon 12 as a hard segment [UBE PAE 1 manufactured by Ube Industries, Ltd.]
200S, MP: 157 ℃, Specific gravity: 1.17, MFR: 6 ~ 13 (190 ℃)]
And 24% by weight of acetylene black are mixed and kneaded using a twin-screw kneading extruder to produce pellets of a polyether polyamide resin containing a conductive agent. Next, the obtained pellets were dried, and inner-sized at an extrusion temperature of 160 ° C. and a take-up speed of 1.2 m / min using a single-screw extruder equipped with an annular die for tube extrusion having a slit width of 1.5 mm, and air-cooled. A tube of a polyether amide was produced while avoiding active stretching. The resulting polyetheramide tube has a thickness of 1
It was a tubular film (tube) having an extremely uniform and smooth surface state of 00 ± 5μ and an outer diameter of 10 mmφ.

This tube is cut into a length of 350 mm,
As a result of measuring the surface resistance value, the resistance value was 2 (± 0.
2) It was × 10 ⁷ Ω / □, and the tube had a stable and uniform resistance value in which no substantial difference was found in the resistance value even when the applied voltage was changed or the measurement location was changed. Using this tube, a charging roller type electrophotographic copying machine as shown in FIG. 1 was produced. That is, the produced tube (hereinafter referred to as tube 1) was cut into a length of 330 mm, and a conductive sponge rubber roll (surface having a diameter of 7 mmφ and a length of 330 mm obtained by winding a conductive sponge rubber around an aluminum tube as a core material) was used. The charging roll was inserted into the hardness shore A10) and the tube was mounted in a suspended state. An electrode for rotating contact was provided at the end of the aluminum tube as a core material of the charging roll, and a lead wire was drawn out and connected to a variable DC power supply via a voltmeter 4a.

The charging roll and the photosensitive drum 3 (an OPC drum, the photosensitive surface of which is coated with a thin polycarbonate film) are set up in the arrangement shown in FIG. 1, but the gap between the roll and the drum is set. A voltage of 1.5 KV is applied from a variable DC power supply, and the tube mounted in a suspended state on the charging roll is attracted to the photosensitive drum by electrostatic attraction, and comes into contact with a contact width of 3 to 5 mm (gap). ) And set. (The gap set in this way is about 1m
In this apparatus, the charging roll was a free-rotating mechanism, and was rotated in synchronization with the rotation of the photosensitive drum.

In order to evaluate the charge transfer / transfer capability of the charging roller-photosensitive drum of the charging roller type electrophotographic copying machine set as described above, the potential charged on the drum was measured under the following measurement conditions, and the performance was evaluated. Was evaluated.
That is, in order to evaluate the charging ability of the photosensitive drum, the exposing device 5, the developing device 6, and the transfer roll 7 are stopped, and the photosensitive drum 3
At a surface speed of 24 mm / sec.
After applying a voltage of 1.5 KV to confirm that the tube of the piezoelectric roll was in suction contact with the photosensitive drum with a contact width of 3 to 5 mm, the potential of the photosensitive drum was measured with a voltmeter.
The measurement results are as follows: voltage application starts, that is, the charging potential at the start of charging: 470 to 480 V, and the charging potential after 5 hours of continuous rotation: 470 to 480 V.
It was confirmed that the photosensitive drum has a stable charge transfer ability.

Next, the copying performance of this apparatus was evaluated under the following conditions. That is, using a halftone image (A4) of 100 lines and 90% as a copy original, the functions of the exposing device 5, the developing device 6 (toner black) and the transfer drum 7, which were stopped in the previous test, are restored. The photosensitive drum 3 is rotated at the same applied voltage and operating speed as in the above test, and
(A4) was supplied, a continuous copy test was performed, and an image quality test of a copied image was performed. First, copy environment conditions: room temperature 20 ° C, R
Continuous copying of 18,000 sheets at 45% H
Samples of the 0th, 5,000th, 10,000th and 15,000th copies were extracted, and image quality checks such as the reproduction fidelity of halftone dots and the density thereof were performed. With respect to the image quality evaluation results obtained by performing a comparison test using the original document and the 100th copy sample as comparison standards, the extracted samples at any time had the same image quality such as halftone dot reproduction fidelity and density, and satisfactory results were confirmed.

Next, in order to check the influence of the copying environment on the copying apparatus, the test was completed by a continuous copying test of up to 18,000 sheets.
The RH was changed to 80%, and continuous copying of 2,000 sheets was carried out in the same manner. A sample of the 2,000th copy was sampled, and a standard sample (the original and 100%) of the image quality evaluation test in the above evaluation test was performed. The results of the evaluation test comparing the image quality with the (second copy sample) confirmed that the image quality was the same, such as the dot reproduction fidelity and density, and that copying could be performed without affecting the copying performance even under high temperature and high humidity environmental conditions. did it.

Further, the copying machine is stopped, the power supply is turned off, the charging roll is taken out, the charging tube 1 is taken out from the guide roll 2 around which the conductive sponge is wound on the aluminum tube, and the surface state of the tube is observed using a microscope. Then, the charged tube 1 was checked for damage (existence of surface roughness, presence of cracks, etc.) due to the application of high voltage, but no abnormalities were found and the external dimensions were 10 mm.
There was no change in φ. Further, the surface resistance was measured again, and the resistance was 2 (± 0.2) × 10 ⁷ Ω /.
It was □, which was the same as before the test, and it was confirmed that no damage was caused by the running test. As a result, it was confirmed that this copying apparatus was a copying apparatus having excellent performance that could withstand continuous operation without undergoing a temporal change in a practically operable working environment and could perform stable high-quality copying. .

Comparative Example 1 A charge roll tube was manufactured by changing the acetylene black content of the polyamide elastomer tube for a charge roll of Example 1 to 4% by weight and 31% by weight (that is, the charge roll tube). The effect of the surface resistance of the charging roll on the copying performance was examined and evaluated under the same conditions except for changing the surface resistance. The results of measuring the surface resistance of each of the manufactured charging roll tubes show that the acetylene black content was 4%.
10 ² Ω / □ for the charging roll tube (hereinafter referred to as ratio 4%) and 10 ¹⁴ Ω / □ for the charging roll tube also changed to 31% by weight (hereinafter referred to as ratio 31%). Met. In the case of the [31% ratio] tube, the surface condition was slightly changed, probably because the amount of acetylene black added was too large.

Using this comparative sample, the charge transfer / transfer capability between the charging roll and the photosensitive drum was evaluated in the same manner as in Example 1. In the case of a charging roll using a [ratio of 4%] tube, the charge roll was placed on the photosensitive drum. Charge is 50-100
The required charging potential was not obtained at V, and some heat generation was observed.
[Ratio 31%] In the case of a charging roll using a tube, although a predetermined charging potential was obtained, there was unevenness in the surface state due to lack of smoothness, and there was unevenness in the charging potential depending on the location, and a uniform charging state was secured. could not. Thus, [ratio 4
%] And [31% ratio], the charge transfer / transfer capability of the charge roll-photosensitive drum as described above can be obtained, and the copy test is not performed because it is not worth performing the copy test. Was.

Example 2 The same polyether polyamide resin powder as used in Example 1 [UBE PAE 1200S manufactured by Ube Industries, Ltd.] was used, and only the amount of acetylene black added was changed to 17% by weight. , Likewise mixing, kneading,
Pelletizing was performed, and using the same extruder as in Example 1, changing only the spinning-drawing conditions, the outer diameter was 15 mmφ,
An 83 μm thick polyether polyamide tube 11 for a charging roll was obtained. This tube was cut into a length of 380 mm, and the surface resistance was measured. As a result, the resistance was 5 (±
0.5) × 10 ⁷ Ω / □, and it was a tube having a stable and uniform resistance value in which no substantial difference was found in the resistance value even when the applied voltage was changed or the measurement location was changed.

This tube 1 cut to a length of 330 mm
1 was made of an aluminum tube as a core material and conductive sponge rubber was wound around the outer diameter of 14.5 mm in diameter and 330 m in length.
m, and inserted into a guide roll having a surface hardness (Shore A35), heated, and fitted and adhered to the guide roll of the core material to produce a charge roll. A charge roller type electrophotographic copying machine having specifications as shown in FIG. And adjusting the contact pressure between the charging roll and the photosensitive drum of the device to a contact width of 3 to 5 mm.
After setting, a performance evaluation test was performed in the same manner as in Example 1. In this apparatus, the charging roll was designed to rotate synchronously with the rotation of the photosensitive drum by a free rotation mechanism.

Transfer of charge from photosensitive roll to photosensitive drum
The results of the transfer performance evaluation were as follows: charging potential at the start of voltage application, that is, at the start of charging: 478 to 487 V, and charging potential after continuous rotation for 5 hours: 475 to 490 V. The ability to give and receive was shown. Next, a copy performance test was performed under the same conditions as in Example 1. However, in the test of the present embodiment, a depth of 10 μ
Four 00μ pinholes were opened and placed in a row. 2
The test results at 0 ° C. and RH 45% atmosphere showed that the samples taken at any time had the same image quality as the dot reproduction fidelity and density, and satisfactory results were confirmed. No image defects due to pinholes were found. In addition, the test results in a high-temperature and high-humidity environment of 40 ° C. and an RH of 80% atmosphere showed no problem, and it was confirmed that the copying environment could be copied without affecting the copying performance.

[Comparative Example 2] The copying performance under the two conditions of Example 2 in which only the contact width between the charging roll and the photosensitive drum was changed to 0.9 to 1.2 mm and 8.5 to 9 mm,
The test was performed at 20 ° C. in an atmosphere of 45% RH. The performance evaluation results show that in the case of a contact width of 0.9 to 1.2 mm,
The fidelity and sharpness of the image were slightly inferior to those in Examples 1 and 2, and the pinhole formed in the photosensitive drum was copied in a slightly pale black color. The contact width is 8.5-9m
m, the resolution of the image slightly decreased from about 15,000 copies. At 20,000 copies, the overall black density was low and seemed to be faint. -It was shown that the contact width between the photosensitive drums was inappropriate and the copying performance was poor. In the above performance evaluation, the surface resistance value was measured by connecting electrodes to both ends of the test piece sheet and connecting them to a resistance measuring device “Hiresta” manufactured by Mitsubishi Yuka Co., Ltd. via lead wires, and applying an applied voltage of 100, 250, 50.
The voltage was applied while changing the voltage to 0 V (DC), and the resistance values at 10 measurement locations were measured, and the measured values were averaged to obtain a surface specific resistance value.

[0057]

Since the present invention is configured as described above, it has the following effects. The charge roller-photosensitive drum by adopting a charge roller type electrophotographic copying machine that uses a polyamide elastomer with excellent charge performance, good charge transfer / transfer efficiency, and appropriate hardness, flexural modulus and compression elasticity for the charge roll. It is possible to carry out the contact between the contact surfaces with a weak contact pressure, thereby increasing the durability of the device and enabling a stable long-running traveling.

The surface resistance of the charging roll can be maintained stably, the charge transfer / transfer efficiency between the charging roll and the photosensitive drum is good, and a stable, high-fidelity, long-run copy of a sharp image can be realized.

Since the transfer and transfer of charge to and from the photosensitive drum are performed by surface contact between the charging roll and the photosensitive drum, the amount of ozone generated during operation (copying operation) is greatly reduced, and the degree of environmental pollution is significantly improved.

The occurrence of image defects is reduced even if there is a pinhole on the surface of the photosensitive drum.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view of a charging roller type electrophotographic copying apparatus of the present invention, particularly, a schematic side sectional view showing an arrangement relationship between a form of a charging roller and a photosensitive member.

FIG. 2 is a partial cross-sectional view illustrating another arrangement relationship between a form of a charging roller and a photoconductor.

FIG. 3 is a partial cross-sectional view showing still another positional relationship between the form of a charging roller and a photoconductor.

FIG. 4 is a partial cross-sectional view showing still another positional relationship between the form of a charging roller and a photoconductor.

FIG. 5 is a partial side sectional view of a conventional charging roller type electrophotographic copying apparatus.

[Explanation of symbols]

1, 11, 13, 15: Endless tubular film (tube) 2, 10, 12, 14: Conductive sponge roll 3: Photosensitive drum 4: Variable DC power supply

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H003 AA05 AA18 BB11 CC05 DD03 EE11 3J103 AA02 AA51 FA12 GA02 GA52 GA57 HA03 HA12 HA18 HA20 HA22 HA46 4F213 AA29 AA32 AA45 AB18 AD03 AD18 AG14 AH81 WA97 WB01

Claims (4)

[Claims] 1. A charging roller type electrophotographic copying machine, wherein said charging roller is an endless tubular film of a polyamide elastomer having a surface resistance value of 10 ³ to 10 ¹³ Ω / □, and a photosensitive member at the time of copying. A charging roller type electrophotographic copying apparatus, which is provided so as to have a contact width of 1.5 to 7 mm. 2. The charging roller type electronic device according to claim 1, wherein the endless tubular film of the polyamide elastomer is a charging roller suspended from a conductive roller obtained by winding a conductive foam on a metal core roller. Photocopier. 3. The charging roller type electrophotographic copying apparatus according to claim 1, wherein the endless tubular film of the polyamide elastomer contains 5 to 30% by weight of carbon black. 4. The polyether block amide elastomer according to claim 1, wherein the endless tubular film of the polyamide elastomer is a polyether block amide elastomer composed mainly of a nylon 12 segment and a segment composed of polyalkylene glycol. A charging roller type electrophotographic copying machine as described in the above.